This application seeks to compare the neurocognitive functioning of attention deficit/hyperactivity disorder (AD/HD) subtypes: predominantly inattentive (IN), predominantly inattentive and predominantly hyperactive-impulsive combined (CB), introduced by the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), as well as a normal control group with respect to attention, memory, inhibitory control, and executive functions. These measures have been selected to maximize the likelihood of identifying the neuropsychological processes and particular brain regions that may mediate the specific deficits.